Patients who have experienced atrial or ventricular fibrillation or who meet a risk profile for atrial or ventricular fibrillation can receive an implantable defibrillator. When an implantable defibrillator identifies the presence of an atrial and/or ventricular fibrillation, the device delivers one or more high energy electrical pulses to the patient to stop the fibrillation and allow the heart to reestablish a normal sinus rhythm.
Ventricular fibrillation is life threatening and requires immediate delivery of defibrillation to terminate the fibrillation. Delivery of high energy atrial defibrillation is also effective to terminate atrial fibrillation; however, atrial defibrillation s often not life threatening. Thus, immediate delivery is not always required. Even so, atrial fibrillation often affects the quality of life of the patient due to the reduced hemodynamic performance of the heart. For those patients having frequent or chronic atrial fibrillation, high defibrillation frequency and the associated discomfort and anxiety is a major deterrent to therapy acceptance.